During insertion or removal of substrates from a substrate container, such as front opening wafer containers, traces of dust, gaseous impurities, or increased humidity can be introduced into the substrate container, adversely affecting product yield of the resident wafers. Accordingly, there is an increased demand for controlling the environment within these transport containers during substrate handling to achieve or maintain a high level of cleanliness.
A microenvironment within a substrate container is typically purged using an inert gas that is injected into the interior of the container through an inlet port causing the air within the container to exit through an outlet port. Systems and methods of delivering purge gas into the container have been designed to provide the improved environment within the container. See, e.g., U.S. Pat. No. 6,221,163 to Roberson et al. (“Roberson”), disclosing a system and method for molecular contamination control permitting purging a container to desired levels of relative humidity, oxygen, or particulates. See also, e.g., U.S. Patent Application Publication No. 2012/0297981 to Burns et al. (“Burns”), disclosing a purge gas inlet port that is be fitted with a tower for vertical distribution the flow of the gas to provide an even distribution of the purging gas within the microenvironment.
The aforementioned references are designed for control of an enclosed microenvironment. That is, conventional equipment and methods that address microenvironment control of substrate containers assume that an opening through which substrates are loaded and unloaded is sealed off by an access door. These systems do not address the intrusion of ambient air into the substrate container during insertion or removal of substrates, i.e., when the access door is removed and the opening is exposed. Such intrusion of ambient air can adversely affect the yield of the resident substrates, even when the ambient environment is that of a clean room.
Additionally, these references do not address the connections between a diffuser tube and an upwardly facing fitting of a purge port assembly. Such connections need to be robust and the port assembly needs to be low profile so as to not interfere with the wafer slots. An improved purging apparatus and method that addresses the issue of ambient environment encroachment when the substrate container is opened to the ambient environment would be welcomed.